Start with the facebook and try to engage the audience by sharing relevant content. The best practice would be to share some viral videos and pictures of your niche( from websites like viralizeed) so that people will start taking more interests in your posts and you can easily get benefit from it .
If your work is attractive than people comes to you you should use better strategies to get more followers.
I would recommend weplugit.com to exchange tumblr and twitter follower exchange. It is free to signup. If you follow someone, people will always follow you back.
Now a days social media marketing have a great priority so you can do it but then you have to work for your targeted traffics. When you will announce about your product then you will try to provide your product related content. What about your business?
Best idea is to follow pages and groups which are related to your niche and join the conversations that occur and perticipate there, try helping others and provide solutions for them that is only if you know the solution, but still try talking to that person in problem, maybe you already have a problem which you haven't realized yet. Build connections, you will not only get more customers, you will get new better supplier chains, better way to optimize your business, new business ideas and a hell lot more. Oh yeah by the way, link your website to the social media, and if your website has the contant that has solution to people's problem in social networking groups, you surely can recommend them to read or view or listen (depending on your content) the specific content on your website. If its helpful to them they will be back for more on your website. I hope this helped!
Twitter can give you a straight connection to the people in your target industry. So, make a Twitter account for your business, find the movers and shakers in your industry, and try to create a connection. Sending a short and simple personal tweet can be a great way to get noticed.